Unit II. СELL Text 2.1 Cell Theory
■ Essential targets
By the end of this text you should be able to:
● describe the main ideas of the cell theory
● compare the structures of animal and plant cells
as seen with a light microscope.
Pre-reading
■ With a partner consider the following questions and try to answer them. Then quickly scan the text to check your answers.
What is a cell?
Who discovered cells?
Do plant cells differ from animal cells?
■ Read the given text and make your essential assignments:
Cells were discovered in 1665 by the English scientist and inventor Robert Hooke. Hooke designed his own compound light microscope to observe structures too small to be seen with the naked eye. Among the first structures he examined was a thin piece of cork (the outer surface of bark from a tree). Hooke described the cork as being made of hundreds of little boxes, giving it the appearance of a honeycomb. He called these little boxes cells. It soon became clear that virtually all living things are made of cells, and that these cells have certain features in common.
The cell theory
The concept that cells are the basic units of life became embodied in a theory called the cell theory, which embraces the following main ideas:
cells form the building blocks of living organisms
cells arise only by the division of existing cells
cells contain inherited information which controls their activities
the cell is the functioning unit of life; metabolism (the chemical reactions of life) takes place in cells
given suitable conditions, cells are capable of independent existence.
A typical animal cell
The structure of a typical animal cell:
the cell has a cell surface membrane which encloses the cell contents
the contents consist of a central ball-shaped nucleus surrounded by material called cytoplasm
the nucleus contains a fibrous material called chromatin
this condenses to form chromosomes during cell division
chromatin contains DNA, the material which controls the various activities inside the cell
scattered within the cytoplasm are mitochondria, small rod-like structures. They have been described as the “power-houses” of the cell because they supply energy.
smaller dots within the cytoplasm are particles of stored food. Many consist of glycogen, which is a food storage polysaccharide.
A typical plant cell
Like an animal cell, a typical plant cell has a cell surface membrane, cytoplasm, and a nucleus. However, plant cells differ from animal cells in several ways:
most plant cells have a large sap-filled cavity called the vacuole. Sap is a watery fluid containing salts and sugars. The vacuole surrounded by a membrane called the tonoplast.
the cytoplasm contains starch grains, the food storage products of plants
many plant cells have chloroplasts in the cytoplasm. These contain the pigments used in photosynthesis. Chlorophyll, which is green, is the main pigment. Chloroplasts occur only in the parts of plants exposed to light – the green parts. They are absent from underground structures such as roots.
■ Glossary of essential terms for you to know
№
|
English term
|
Russian equivalent
|
1
|
cork
|
пробка
|
2
|
honeycomb
|
соты пчелиные
|
3
|
cell
|
клетка
|
4
|
to embody
|
воплощать, олицетворять
|
5
|
to enclose
|
окружать
|
6
|
contents
|
содержимое
|
7
|
surface
|
поверхность
|
8
|
membrane
|
мембрана
|
9
|
nucleus
|
ядро
|
10
|
to surround
|
окружать
|
11
|
cytoplasm
|
цитоплазма
|
12
|
fibrous
|
волокнистый, фиброзный
|
13
|
division
|
деление
|
14
|
to scatter
|
разбрасывать, рассыпать
|
15
|
to supply
|
обеспечивать, снабжать
|
16
|
storage
|
хранение
|
17
|
sap
|
сок растения
|
18
|
cavity
|
полость
|
19
|
starch
|
крахмал
|
20
|
root
|
корень
|
21
|
compound
|
сложный
|
22
|
to observe
|
наблюдать
|
23
|
to examine
|
исследовать
|
24
|
feature
|
черта
|
25
|
suitable
|
подходящий
|
26
|
existence
|
существование
|
27
|
fluid
|
жидкость
|
28
|
grain
|
зерно
|
■ Your Essential Assignments
I. Quick check
1. Briefly state the main concept of the cell theory.
2. List the features:
a) that only animal cells have
b) that only plant cells have
c) that both animal and plant cells have.
II. Fill in the missing words:
Term (verb)
|
Noun
|
Adjective
|
exist
|
.......
|
.......
|
store
|
.......
|
.......
|
form
|
.......
|
.......
|
divide
|
.......
|
.......
|
act
|
.......
|
.......
|
suit
|
.......
|
.......
|
differ
|
…..
|
……
|
III. Use monolingual English dictionary and write down what could the words given below mean:
surface, honeycomb, cavity, plant, sap.
IV. Match these words with their definitions:
1.
|
cell
|
A.
|
a scientific instrument that makes extremely small things look larger
|
2.
|
to observe
|
B.
|
the amount of a substance that is contained in something
|
3.
|
microscope
|
C.
|
the contents consist of a central ball-shaped nucleus surrounded by material
|
4.
|
metabolism
|
D.
|
parts of plants that can you eat but cannot digest, which help food to move quickly through your body
|
5.
|
independent
|
E.
|
the central part of an atom, made up of neutrons, protons, and other elementary particles
|
6.
|
contents
|
F.
|
to watch something or someone carefully
|
7.
|
nucleus
|
G.
|
in something
|
8.
|
cytoplasm
|
H.
|
the act of keeping or putting something in a special place while is not being used
|
9.
|
fibre
|
I.
|
the chemical reactions of life
|
10.
|
inside
|
J.
|
existing separately and not connecting with or influenced by any others
|
11.
|
storage
|
K.
|
the green-coloured substance in plants
|
12.
|
chlorophyll
|
L.
|
the smallest part of a living thing that can exist independently
|
V. Find English equivalents to the following word combinations:
№
|
Russian term
|
English equivalent
|
1.
|
ученый и изобретатель
|
|
2.
|
слишком маленький, чтобы увидеть
невооруженным глазом
|
|
3.
|
сделаны из клеток
|
|
4.
|
живые организмы
|
|
5.
|
деление существующих клеток
|
|
6.
|
наследственная информация
|
|
7.
|
подходящие условия
|
|
8.
|
окружает содержимое клетки
|
|
9.
|
во время деления клетки
|
|
10
|
снабжать энергией
|
|
11
|
отличаться от ч.-л.
|
|
12
|
содержать соли и сахара
|
|
13
|
быть окруженным мембраной
|
|
14
|
пигменты, используемые в фотосинтезе
|
|
VI. Give Russian equivalents to the following English terms:
№
|
English term
|
Russian equivalent
|
1
|
a compound light microscope
|
|
2
|
to serve structures
|
|
3
|
to have certain features in common
|
|
4
|
the basic units of life
|
|
5
|
the cell theory
|
|
6
|
the functioning unit of life
|
|
7
|
it takes place in cells
|
|
8
|
independent existence
|
|
9
|
a typical animal cell
|
|
10
|
a cell surface membrane
|
|
11
|
а ball-shaped nucleus
|
|
12
|
a fibrous material
|
|
13
|
inside the cell
|
|
14
|
small rod-like structures
|
|
15
|
a food storage
|
|
16
|
a sap-filled cavity
|
|
17
|
starch grains
|
|
18
|
exposed to light
|
|
VII. Find synonyms among the pool of words:
Pool of words
|
Synonyms
|
1) 1.occur /2.scatter /3. take place /4. spread
|
|
2) 1.cavity /2.sap /3.juice /4.contents /5.hole /6.ingredients
|
|
3) 1.nucleus/2.division/3.core/4.naked/5.separation/6. bare
|
|
4) 1.unit /2.part /3.fluid /4.grain /5.solution /6.corn
|
|
VIII. Answer the following questions. Use all information given before:
When were cells discovered?
How did Robert Hooke discover cells?
What is called the cell theory?
What are the main ideas of the cell theory?
What is the structure of a typical animal cell?
How do plant cells differ from animal cells?
IX. Match the sentence halves. Make complete sentences:
1.
|
Hooke designed his own compound light microscope
|
A.
|
a membrane is called the tonoplast.
|
2.
|
The concept that cells are the basic units of life
|
B.
|
of living organisms.
|
3.
|
Cells form the building blocks
|
C.
|
which controls their activities.
|
4.
|
Cells arise only by
|
D.
|
to observe structures too small to be seen with the naked eye.
|
5.
|
Cells contain inherited information
|
E.
|
called chromatin.
|
6.
|
The contents consist of a central ball-shaped nucleus
|
F.
|
the division of existing cells.
|
7.
|
The nucleus contains a fibrous material
|
G.
|
called the vacuole.
|
8.
|
Chromatin contains DNA, the material which controls
|
H.
|
became embodied in a theory called the cell theory.
|
9.
|
Most plant cells have a large sap-filled cavity
|
I.
|
surrounded by material called cytoplasm.
|
10.
|
The vacuole surrounded by
|
J.
|
in the cytoplasm.
|
11.
|
Many plant cells have chloroplasts
|
K.
|
the various activities inside the cell.
|
12.
|
Chloroplasts occur only in the parts of plants
|
L.
|
exposed to light – the green parts.
|
X. Read and translate the short text without any dictionary:
Fact of life:
Robert Hooke described his observations of the cork cells: “I counted several lines of these pores, and found that there were usually about three-score of these small Cells placed end-ways in the eighteenth part of an inch in length, whence I concluded that there must be near eleven hundred of them, or somewhat more than a thousand in length of an inch and therefore in a square inch above a Million, or 1 166 400, and in a Cubick Inch, above twelve hundred million, or 1 259 712 000, a thing almost incredible, did not our Microscope assure us of it by ocular demonstration.
XI. Food for thought: Suggest why red blood cells appear to contradict the cell theory.
|
